The use of opacifiers to enhance the appearance and visibility of coloring compositions is well known. When coloring compositions containing an opacifier are applied to opaque surfaces (e.g., paper, walls, whiteboards, etc.), the opacifier brightens and intensifies the images produced by the composition. When coloring compositions containing an opacifier are applied to transparent surfaces, the opacifier enhances the visibility of the writings through increased light scattering. Inorganic pigments, such as titanium dioxide, have commonly been used in paints as an opacifier.
Coloring compositions containing a conventional opacifier, however, suffer from a variety of well-known deficiencies that render them unsuitable for use in children's coloring markers. Conventional opacifiers settle-out over time causing writing instruments to clog and resulting in unacceptable variation in the writings. Although valve-type marker systems containing an agitator ball allow the user to redisperse the settled particles, such non-conventional markers are significantly more expensive and cumbersome than traditional capillary delivery systems. The inclusion of thickeners to counteract this settling produces compositions having an unsatisfactory viscosity that cannot be dispensed through capillary-type markers. Finally, opaque inks containing pigments and other resins sometimes render the compositions permanent which is not appropriate for a coloring product primarily used by children who often make stray marks on themselves and surrounding surfaces. As a result of these inadequacies, coloring markers containing conventional opacifiers have not been produced with great success.
Further, even when traditional marker inks containing dyes are stable when stored either tip up or tip down, they produce markings that are transparent when dry. Consequently, writings on transparent surfaces (e.g., windows) or colored paper are difficult to see upon drying.
It is therefore one general object of the invention to provide a water-based coloring composition suitable for use in markers which produces images exhibiting enhanced visibility and stability, suitable for writing on porous and non-porous surfaces.
A further object is to provide water-based coloring compositions which exhibit enhanced visibility and stability on transparent and colored writing surfaces.
A further object is to provide non-toxic coloring compositions which are suitable for use by young children who may make marks on themselves and their clothing.
A related object of the invention is to provide a dry erase coloring composition suitable for use on windows, writing boards, whiteboards and other non-porous surfaces.
These and other objects and advantages of the present invention, as well as additional inventive features, will be apparent to those skilled in the art from the following description of the invention and the appended claims.